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donmilne

Fine tuning the bed levelling procedure.

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I don't think think this feature exists already...

Suppose I've just gone through the bed levelling exercise. I've done a test print and while I'm happy that the bed is level, I'm unhappy with the precise amount of "squish" in the first layer. E.g. the filament is getting smeared out too much, or else I see distinct cross hatching (not squished enough).

Is there a way to just adjust the stored Z-zero up or down by a fine increment without repeating the whole levelling procedure - which will undoubtedly just get it slightly off again?

If not, could such a feature be added to the firmware?

I'm open to suggestions as to what the appropriate up/down increment would be.

 

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Hi DonMilne

As a UM orginal user I just grab the z axis coupler and turn it the direction I want it to go to do the adjustment while printing. Having something in the software would be nice... In my case the Z axis has some variation so from print to print it might be different.

Eric

 

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The firmware might support this but it might require a custom build. I don't have experience with this but I suggest you review this:

http://airtripper.com/1799/marlin-firmware-home-offset-guide-using-g-code-m206/

You can of course just try the m206. I suspect that changing the offset in one direction increasing or decreasing the Z gap) will work but the other direction may not due to either the software or hardware endstops.

(You can ignore parts about enabling the EEPROM support. I think by default that is already enabled in the UM firmware).

 

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Hi,

It wont address your exact request to "fine tune" the bed level on the fly but the new firmware released here http://umforum.ultimaker.com/index.php?/topic/5935-z-axis-homing-inconsistent-on-um2-workaround-and-patch/page-6&do=findComment&comment=57095 fixes a real issue with maintaining the first print layer height consistency between prints.

Updating the firmware from Cura is really simple.

 

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DonMilne - um1 or um2? The um1 has this feature in the latest firmware but you have to build it yourself. It's exactly the feature you describe. I think it is in the tune menu and called something like z-tweak.

I don't think it's available for um2.

Please update your profile to say what printer/printers you have.

 

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I have a UM2. I don't see anything in my profile to indicate my printer.

I'm afraid that the suggestions of "live" adjustments while printing don't appeal. Because the screws are on the underside of the bed I have trouble wrapping my head around whether a clockwise or aclockwise turn raises or lowers the bed. I prefer to have a direct software adjustment.

 

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I don't see anything in my profile to indicate my printer.

Up on top right corner click on your profile settings. Then in top right corner click big blue button to edit. Then At the bottom is "printer". Fill it in.

 

I have trouble wrapping my head around whether a clockwise or aclockwise turn raises

Me too. And I hate working fast under pressure - I panic. So I think about it before I start the print (lets see I if it's printing lines up in the air I need it closer so loosen so counter clockwise from below).

 

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Well there is a bug in Marlin that is fixed in version (14.07?) and it makes leveling problematic. When you first level it's off by a little and then after you power cycle it's off even more. But the latest Marlin fixes this.

Once you get leveling down good, you probably won't have to level again for months. It tends to be consistent once you get the proper firmware or if you stop using the procedure and only level with the screws.

 

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Since I end up leveling a lot of print beds these days, I've made a point of remembering that 'Right is NOT tight' (contrary to the normal mantra for regular screwdriving).

In other words, turning the front of the thumbscrew towards the right INCREASES the gap between the head and the bed.

When leveling, I also prefer to do it by looking along the glass and noting when the nozzle tip exactly touches its reflection. I level it to that point on the first go round, and then only bother even checking the second pass through if I had to make any significant adjustments on the first pass - otherwise I just click-click-click through those three.

It's important to make sure the nozzle is totally clean before leveling, so you aren't leveling to a blob of plastic, rather than the real tip. Also when adjusting the screws, always adjust until you just get a touch, back off slightly and allow the bed to settle untouched, and then tighten to a touch again.

Another critical factor in bed leveling is that the screws are all positively engaged, and the springs are under proper tension. Since the springs are quite short, and the bed tends to droop a couple of mm or so towards the front, there's actually quite a narrow range in which you can get everything lined up properly.

Before you run the leveling wizard, the rear thumbscrew should be tightened until the wiring terminal block is about 1mm from touching the heavy base plate. From that datum, the gap at the front between the two plates when it's level should be about 12-13mm. In that arrangement, the screws are all well seated and the springs are providing useful tension.

 

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Thanks, but I'd rather this thread didn't drift off into a general bed levelling procedure discussion - I think we've had that discussion before, and I was grateful for it then. Here I'd like to stick to the narrower discussion of how to make minor height corrections after you've done a first test print and seen what the results were.

p.s. Thanks for the tip on how to add my printer to my profile.

 

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There is no start gcode on a Ultimaker². I mean, you can add it manually to the finished gcode, but there's nothing that gets included automatically by Cura. And I think the intent is that you should be able to adjust the bed from the machine end, without adjusting the gcode you already have.

The current bed leveling wizard in the printer allows you to adjust the back height in 0.05mm increments if I remember correctly. Arguably, that's a bit too coarse - certainly for fine tuning, I'd go with perhaps half of that height.

 

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Oh really, I didn't know the UM2 didn't add start or end G code. That changes things completely for UM2 users.

Adjusting things from the machine end are great, as long as it saves the setting. Making that 0.01mm increments would allow users more control indeed.

 

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